I used only making the pitts muffler outlet tubes outlet area abut the same as the original equipment muffler outlet area and mine run very nicely. this is with either a fox r/c long or os f plug, and omega 10% fuel. also do not tune it to have much of a smoke trail - it does need to be a little rich on the top end when taking off as the engine will heat up a bit more in the air and lean out some, but they don't run like saitos. ay least in my experience most saitos like to be what I would call super rich where you can see a heavy smoke trail in the air.

Ed